This does not happen with Debian 9.3 (Kernel 4.9.x). If I partition the devices with one 2GB primary partition and do the same operation but with /dev/nvmeXn1p1 or p2 the timeout does happen on the second partition but not on the first:

It seems that the Proxmox* OS is not running the latest Kernel, we would like to inform you that the Kernel required for the SSD is 4.7 or above due to the NVMe* drivers. That is why with Debian* 9.3 (Kernel 4.9.x) the SSD works.

We recommend you to install the Kernel 4.7 or above for the Proxmox* OS(if available).